Vacuum systems have been commonly used for the removal of ash and similar residue within an incinerator after a burning cycle is completed. However, many such systems operate in a fashion similar to the conventional home vacuum cleaner wherein an electric motor draws air from the suction end of the device, creating a partial vacuum and simultaneously drawing residue into a suitable container. The air is then discharged at the other end of the system and no further use is made of the kinetic energy of this moving air stream.
Aside from wasted energy, this type of system has an additional disadvantage that the suction force is evenly distributed around the inlet in all directions and cannot be directed toward the matter being picked up except by the use of separate manual means.
The first above-mentioned disadvantage has been at least partially overcome in vacuum cleaning apparatus employing "closed circuit" systems wherein residual matter is picked up an air stream and is removed by a cyclone filter or the like, with the air stream then being redirected back through the system for reuse. However, a serious problem still exists in a closed circuit system of this type. It has been found that when the apparatus is used to clean residue from the bottoms of devices such as incinerators, for example, some of the residue is in the form of relatively large agglomerations of congealed particulate which will not be removed through one or more relatively small suction pipes.